Sphere Online Judge (SPOJ)

list of classical problems

ID	NAME	USERS	ACC %	DIFFICULTY C I
3970	Convert to Decimal Base System	55	37.23	17 17
3972	Stargates	47	13.58
3981	Shortest Regular Bracket	81	33.92
4003	Subway planning	43	18.98
4004	Exploding CPU	144	46.24
4008	Con Voi	9	57.69
4010	Chặt cây	10	21.31
4021	Bipalindrome	183	30.77
4034	Pizza Delivery	53	16.55
4052	Game	75	29.27
4060	A game with probability	208	21.97
4062	Rob Mini-Safe	113	39.49
4069	Morphing is Fun	29	17.82
4070	Two Professors	102	13.96
4083	Tele Broadcast	67	50.26
4097	Locomotive	35	38.30
4142	Ellipse	19	8.73
4154	IZBORI	38	26.51
4156	PLAHTE	68	35.51
4160	A1 Road	88	50.21
4178	Distance on a square lattice	129	54.23
4185	Cube	56	35.35
4188	Amazing equality	41	13.46
4189	Landing	5	2.73
4202	Brackets Parade	237	44.95
4210	Fast Maximum Matching	16	45.65
4211	Fast Maximum Flow	19	23.81
4212	Another Longest Increasing Subsequence Problem	13	42.11
4225	Payment System	29	66.07
4275	rotate it	40	55.70
4278	Battlefield	6	38.71
4307	Stamps	31	40.66
4308	Byteantean towns	56	24.16
4309	Circular game	34	19.90
4311	Quasi-template	59	33.98
4324	The fate of the pineapple	44	28.37
4361	Connected Points	9	30.77
4378	Twofive	64	26.30
4407	Counting Arborescence	101	33.94
4410	Repair the Door	60	22.63
4411	Counting Expressions	29	34.83
4414	Highway	57	21.71
4420	Counting Graphs	72	36.33
4421	Irreducible polynomials over GF2	63	17.89
4453	Bouncing Balls II	226	28.02
4455	Going to the Movies	88	36.56
4459	Muzidabutur	34	27.56
4461	A Famous Airport Manager	26	16.97
4477	Flower growing	115	22.02
4478	Counting Expressions II	14	18.56